Pressure responsive rheostat



March 2s, 1939. M. KLEIN ET AL 2,152,262

' PRESSURE RESPONSIVE RHEOSTAT Filed Sept. :3, 1935 ?atented Mar. 28, 1939 UNITED STATES PATENT osslcs KBESSURE BESPONSIVE RHEOSTAI Pennsylvania Application September 3, 1935, Serial No. 39,082

6 Claims.

The present invention relates to improvements in pressure responsive rheostats, and, more-particularly, concerns s. pressure responsive rheostat designed for ready application at any point of a. fluid system under pressure and for convenient inclusion in an electrical circuit including an indlcstor designed to show the pressure at said point.

It is frequently desirable to indicate electrically at a, remote point or observation the pressure existing in s fluid system. This can readily he socomplish'ed by employing a variable rheostst the efiective resistance of which is automatically varied with the pressure in the system, such vertstiou in resistance regulating the current flowing in so electrical circuit including an indicator showing the current flowing in said circuit. The indicator thus is actuated simultaneously with variations in the resistance which responds to pressure changes. The electrical indication of pressure at 2, remote point may be employed, for example, in an automotive vehicle, and is edvontsccous, when so used, inasmuch as the pressure measuring device may be located adjacent the source or" pressure or at any desirable point in the oil or like system, end the indicator disposed on the dash, where it is readily visible, the indicator and pressure measuring device being connected only by electrical conductors. fiuch arrangement avoids the use of conduits extending to the dash ordinarily employed cud required when u direct pressure measuring cud indicating gauge is lo outed on the dash of on automobile.

The primary object or the present invention resides in the provision oi a combined rhecstst' and pressure measuring device oil at unitary charscter capable of ready application and satisfactory use st any court of s fluid system suicjected to varying pressures and for convenient insertion in an electrical circuit including an indicstor or" current flowing therein.

Another object of the present invention resides in the provision of s. rheostst which is simple, compact and durshle and capable of production at a. low cost.

Still a. further object of the present invention resides in the provision of c rheostet which is designed for actuation in proportion to changes in pressure of a fluid source, and which is designed to be electrically connected to an indicating instrument and to compensate for magnetic peculiarities oithe indicating instrument.

Another object oi the invention is to combine a pressure responsive device, and a rheostst con-' trolled thereby, in a single casing that completely houses the assembly whereby the combined devices may he applied anywhere regardless of the conditions existing at the point or application thereof.

Further objects of the invention will appear in the following detailed description and appended claims when considered in conjunction with the drawing in which:

Figure 1 is s. front elevetloual view of a preferred embodiment of the present invention with the casing cover removed.

Figure 2 is a sectional view taken substantially in line 22 of Figure 1, ports of the structure being shown in elevation to clarify the illustratlon.

Figure 3 is s diagrammatic view illustrating the preferred form oi our invention when emoloyed as part or s system for remote indication of pressure.

Referring now to Figures l and 2, the preferred form oi our invention embodies a casing 23 having a cylindrical wall 22 and a. transverse end wall 23. Mounted within an aperture 24 in cylindrical casing wall 22 is a conventional bindlng post assembly comprising a. post it having 2. head 2'! disposed within casing El and s. shank, 3 8 extending outwardly through aperture M. Threaded on post shoots 23 are nuts ill and 32 which serve to firmly clsmgo one end of an electrical conductor d3 designed to he looped shout shoot: it oetweeu the nuts sud designed for connection with or: external electrical circuit. Au electrically insulating washer lid is disposed concentrically about post 2% between nut 33 and the exterior surface of seeing well Disposed concentrlcslly upon post between head ill thereof and the interior surface oil casing well 22 is 2. second electrically insulating Washer 36 provided with an axially offset portion Bl which extends within aperture '28 of the seeing well. The bindlug post 26 is thus completely insulated from casing 25 and current flowing through conductor 83 to shank 28 and head Ti will be prevented from flowing into casing 2i.

A pressure responsive or measuring device, in-

dicated generally at Al, is mounted upon "transverse casing wall 23 adjacent cylindrical wall 22. This device includes a bracket or socket member 42 secured to casing wall 23 by screw 43 or the like and provided with a tubular extension 44 projecting outwardly from casing 21 through a suitsble aperture (not shown) in wall 23. Bracket 42 is further provided with a post 46 extending into the interior of casing 21. Extension 44, bracket 42 and post 45 are provided with lntercommunieating bores which through extension 44 are placed in communication with a fluid pressure source.

Mounted upon post 49 is one end of a Bourdon tube 49 the interior fluid chamber of which is in communication with the bore in post 45. The free end of Bourdon tube 49 is closed by a cap 41. Bourdon tube 49 is thus adapted for flexing, with consequent movement of the free end thereof, in response to pressure changes at the fluid pressure source in well known manner.

Mounted for rotation upon bracket 42 adjacent casing wall 22 is a sleeve 49 carried by a column (not shown) mounted on bracket 42. On sleeve 49 is rigidly secured a collar 59 carrying a curved crank arm 5| provided with an elongated slot 52. An extension arm 93 having an offset portion 54 is rigidly mounted upon crank arm 5| by means of a screw 99 locked in selective position with respect to slot 52 by means of a nut 59. A nipple 99 formed upon extension arm 59 is designed to extend into slot 52 to prevent rotation of arm 53 about bolt 59 and insure rigid interlocking of crank arm 5| and extension arm 59.

Offset portion 54 of arm 53 carries a pin 9| to which is pivoted one end of a link member 62, the other end of which is pivoted upon a pin 63 carried by Bourdon tube cap 41.

By means of the structure Just described movement of the free end of Bourdon tube 46 is eifective through link 92 to cause rotation of extension arm 53, crank arm 5|, and sleeve 49 as a unit. The effective length of the torque arm formed by crank arm 5| and arm 53 may be varied by loosening screw 55, selectively positioning the screw with respect to slot 92 in crank arm 9| and retightening the screw. In this manner the normal distance from sleeve 49 to the line of force acting through link 62 may be selectively regulated and the magnitude of rotation of sleeve 49 in response to a given movement of the free end of Bourdon tube 46 may be controlled.

Coiled about sleeve 49 between bracket 42 and collar 99 is a helical spring 69, one end of which is secured about a pin 99 formed on bracket 42 and the other end of which bears against the torque arm formed by crank arm 5| and arm 53. Spring 99, which is relatively weak in comparison to the resilience of Bourdon tube 46, is provided for taking up backlash or lost motion in the joints between Bourdon tube tip 41 and crank arm 5|.

A contactor arm 19 comprising dual axially spaced wiper arms 1| and 12 carried by a collar 13 are mounted upon the end of sleeve 49 remote from bracket 42. A screw 14 furnishes an end shoulder for sleeve 49 and holds the sleeve upon a column (not shown) mounted on bracket 42. Intermediate the ends of wiper. arms 1| and 12 is provided a bridge member 15 which is secured to the wiper arms in any suitable manner as, for example, by welding or the like, and which is designed to retain the wiper arms in proper axially spaced relation and to prevent spreading of the extremities 19 and 19 of the wiper arms. The adjacent surfaces of wiper arm extremities 19 and 19 are provided with contact tips 9| and 92 respectively formed of electrically conductive material and designed to contact successive points ona resistor now to be described.

Disposed within casing 2| remote from sleeve 49 and substantially tangent to the path of travel of contactor tips 9| and 92 is a resistance, indicated generally at 99, which is supported upon insulating posts 99 or the like secured to casing wall 29 by means of screws 91 extending through the casing wall and threaded into the posts. The heads of screws 91, which are disposed outside casing wall i2, may be covered by solder 99 or other suitabale material to prevent access to and adjustment of the screws after posts 99 have been assembled within casing 2|. Resistance 99 is secured to insulating posts 96 by means of screws 9| and 92.

Resistance 99 comprises a multiplicity of convolutions or coils of relatively fine resistance wire 93 wound upon a non-conducting card 94 having one end 95 of uniform width, the remote end 99 of the card being of an increased and non-uniform width. The end of coil 93 adjacent the enlarged end 99 of the card is looped beneath the head of bolt 9| to prevent unwinding of the coil. The end turns of coil 92 adjacent uniform end 95 of the card are clamped beneath a clip 99 of conducting material which is bent concentrically about card 94 and which is designed to be clamped beneath the head of screw 92.

A second clip |9| of conducting material is clamped beneath the head of screw 92 and in contact with clip 98. Clip IN is press-fitted securely on one end of a short electrical conductor 92 the remote end of which is secured in contact with bindingpost head 21 by means of solder M4 or the like.

As seen in Figure 2 the wiper arm contact tips 9| and 92 are designed to simultaneously contact the opposite sides of any particular turn of the resistance coil as the wiper arms 1| and 12 pass over the resistance coil during rotation of sleeve 49. Preferably, contact tips 9| and 82 are adapted for movement over the entire surface of the resistance coil, although if desired, movement of the tips 9| and 82 may be restricted to a localized portion of the resistance coil.

From 'the structure thus far described it will be appreciated that current flowing in conductor 33 will be confined within the rheostat unit to a circuit including binding post 26, conductor I92,

resistance coil 93 and contact tips 9| and B2.'

Preferably electrical communication is provided between contact tips 9| and 82 and tubular extension 44, which is grounded, by a path including wiper arms 1| and 12, sleeve 49, bracket 42, and extension 44, which units are formed from electrically conductive material, although such communication may be effected in any other suitable manner.

Current flowing in conductor 39 from an external circuit may therefore pass through a continuous circuit within the rheostat including binding post 26, resistance 89, wiper arms 1| and 12, sleeve 49, bracket 42 and easing 2| to the grounded extension 44.

Figure 3 illustrates a preferred mode of using the combined pressure measuring device and rheostat unit of the present invention. The rheostat is connected in series with an external circuit including an electrical indicating instrument 91 responsive to changes in current flow, and a battery I99 which when used on an automobile is the battery of the car. Conductor 99, which is connected at one end to the binding post 29 of the rheostat unit, is at its other end connected to one terminal of the indicator I91. Within indicator 91 current passes through differential coils (not shown) one of which is grounded as indicated at G1 to the vehicle frame and the other of which is connected by a wire I99 to the vehicle battery III which in turn is by means of a wire "2 grounded as indicated at 0: II

to the vehicle frame. Casing 2i the rheostat unit is by means of tubular. extension 54 grounded as indicated at G3 to the vehicle frame;

with battery I08 impressing a substantially constant electromotive force upon the circuit just described, and with a substantially constant resistance in the external part of the circuit, it will be appreciated that the current flowing in the circuit will be proportional to the effective resistance inserted into the circuit by resistor coil 93 of the rheostat unit.

lhe effective resistance of coil 93 depends, however, upon the position of contacttips 8i and 82 with respect to the resistance coil, the maximum effective resistance existing when the contact. tips are furthest removed from end 96 of the coil.

Resistance coil 93 is enlarged at one end in order that currentfiow within the previously described circuit will increase more rapidly than the rate at which the contactor tips pass over the resistance coil during the period when the upper path oi movement is reached. Such increase in the rate of current iiow is necessary due to peculiarities in the magnetic coils of indicating instrument ifl'l.

If desired the resistance existing between successive turns oi the resistor coil may be varied by altering the shape of the coil for the purpose of compensating for errors in registration of the wiper arms with the resistance coil introduced by independent factors.

Operation oi the rheostate unit will occur in the lollowing manner: Variations in pressure existing at the fluid pressure source will be communicated through the bores in bracket 42 to the Bourdon tube which will he reactively distorted with consequent displacement of the free end of the Bourdon tube. Such movement of the free end of the tube is through link 62 effective to cause rotation of crank arm sleeve 49 and wiper arms ii and I2 as a unit. Contact points at and 82 are consequently reciprocated with respect to resistance coil 83 to vary the effective length thereof which in turn is effective to automatically regulate the current flow within the circuit including indicator to! and battery N8. Indicator it? will be actuated in response to such regulation of current flow and will thus register in response to variations in pressure source through the medium of the pressure responsive rheostat unit.

it will therefore be seen that the present i; vention provides a pressure responsive rheostat which responds accurately to variations in pressure at a iiuid source, which automatically compensates for peculiarities in actuation of the indicating device, and which is compact and efficient in operation.

The invention may be embodied in other speciflc forms Without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope oi the invention being indicated by the appended claims rather than by the foregoing desoription, and all changes which come within the meaning and range of equivalency oi the claims are therefore intended to be embraced therein.

't t 'hat is claimed and desired to be secured by United States Letters Patent is:

l. in a pressure responsive rheostat; a casing including a cylindrical wall and a transverse end wall; a bracket mounted within said casing and with its back against said end wall; a pressure responsive element carried by said bracket and spaced considerably from one portion of said cylindrical wall, said element being uniformly responsive to equal increments of pressure variatlon; a contactor arm pivoted to said bracket and extending, in a plane in front of said responsive element, to a point considerably therebeyond and adjacent said portion of said cylindrical wall; a substantially flat and rectilinear resistance strip including non-uniform resistance areas supported on said end wall and spaced therefrom so as to lie in. the aforementioned plane, said resistance strip extending chordally across said casing beyond the ends oi the are described by the free end oi said contractor arm; said free end of said contractor arm being formed to contact oppositesides of said strip to thereby prevent movement of said free end away from said strip and consequent breaking of said contact; and means interconnecting said arm and said responsive element so that uniform movement of said responsive element causes said free end of said arm to uniformly move along said resistance strip, whereby the effective resistance of said rheostat is non-uniformly varied by equal variations of pressure in said responsive device.

2. In a. pressure responsive rheostat, a casing including a cylindrical wall and an end wall; a bracket member in said casing; a pressure responsive element uniformly responsive to equal increments of pressure variation mounted on said bracket member and adapted to be connected to a source of fluid pressure; a pivot member rotatahly mounted on said bracket; a resistance strip having non-uniform resistance areas supported in said casing, on said end wall, and between said responsive element and a portion of said cylindrical wall; spaced elongated contact elements extending from said pivot member and having free ends contacting opposite sides of said strip; means connecting said free ends at a point adjacent said strip to thereby prevent movement of said elongated contact elements away from said strip and consequent breaking of said contact; means connecting said pivot member and said responsive element so that said pivot is rotated uniformly by said element; whereby uniform variations in the fluid pressure at said source will cause said contact points to move uniformly along said strip and non-uniformly vary the effective resistance of said rheostat. and means to connect one end of said strip and said contact elements in an electric circuit.

3. In a pressure responsive rlieostat, a casing including a cylindrical wall and a transverse end wall; a bracket mounted within said casing and with its back against said end wall; a pressure responsive element carried by said bracket and spaced considerably from one portion of said cylindrical wall; a contactor arm pivoted to said bracket and extending, in a plane in front of said responsive element, to a. point considerably therebeyond and adjacent said portion of said cylindrical Wall; a substantially flat and rectilinear resistance strip supported on said end wall; and spaced therefrom so as to lie in the aforementioned plane, said resistance strip extending chordally across said. casing beyond the ends of the are described by the free end of said contactor arm; said free end of said contactor arm being formed to contact opposite sides of said strip to thereby prevent movement of said free end away from said strip and consequent breaking of said contact; and means interconnecting said arm and said responsive element so that movement of said element causes said free end of said arm to move along said strip, whereby the effective resistance of said rhecstat is varied by variations oi pressure in said responsive element.

4. In a pressure responsive rheostat; a casing including a cylindrical wall and an end wall; a bracket member in said casing; a pressure responsive element mounted on said bracket and adapted to be connected to a source or Iiuid pressure; a pivot member rotatably mounted on said bracket; a redstance element supported in said casing, on said end wall. and between said responaive element and a portion of said cylindrical wall; spaced elongated contact elements extending from said flvot member and having free ends contacting opposite sides of said strip; means connecting said free ends at a point adjacent said strip to thereby prevent movement of said elongated contact elements away from said strip and consequent breaking or said contact; means connecting said pivot member and said responsive element so that said pivot is rotated by said responsive element, whereby variations in the fluid pressure will cause said contact points to move along said strip and vary the eflective resistance of said rheostat: and means to connect one end of said strip and said contact elements in an electric circuit.

5. In a pressure responsive rheostat for use with an indicating instrument having non-uniiorm magnetic characteristics; a casing including a cylindrical wall and an end wall; a bracket mounted within said casing and with'its back against said end wall; a pressure responsive element carried by said bracket and spaced considerably from one portion of said cylindrical wall, said element being uniformly responsive to equal increments of pressure variation a contactor arm pivoted to said bracket and extending, in a plane in front of said responsive element, to a point considerably therebeyond and adjacent said said casing; a substantially 1m and roctilinear resistance strip, including non-uniform resistance areas, supported at its ends on said post members; said resistance strip extending chord ally across said casing beyond the ends 0! the are described by the free end of said contactor arm; said free end of said arm being formed to contact said strip; and means interconnecting said arm and said responsive element so that uniform movement of said responsive element causes said tree end oi said arm to uniformly move along said resistance strip, whereby the effective resistance of said rheostat is non-uniformly varied by equal variations of pressure in said responsive device. 7

6. In a pressure responsive rheostat, a casing including a cylindrical wall and a transverse end wall, a bracket member mounted within said casing, a pressure responsive element secured to said bracket and adapted to be connected to a source of fluid pressure, a pivot member rotatably mounted on said bracket adjacent said responsive element, a resistance strip including a nonuniform resistance area positioned within said casing, a contact element fixed to said pivot member and contacting said resistance strip, an arm on said pivot member, and means connecting said arm to said responsive element whereby variations in fluid pressure at said source will cause uniform rotation of said pivot and uniform movement of said contact along said resistance strip to vary the effective resistance of said rheostat, said connecting means being adjustable radially of said arm to adjust the amount of contact movement to be effected by a unit change in pressure.

MAXIMILIAN KLEIN. BERNHARD WILLACH. 

